International Journal of Medical Microbiology Supplements最新文献

Human granulocytic ehrlichiosis (HGE) is a tick — borne zoonosis caused by Anaplasma phagocytophilum. A MEDLINE literature search revealed that the European story of HGE began in 1995 with an article on the presence of serum antibodies to A. phagocytophilum. At present, there is seroepidemiological information indicating the presence of infection with HGE agent(s) for several European countries; seroprevalence rates range from zero or very low to up to 28%. The proportion of seropositive persons increases with age and is higher in persons exposed to ticks. Knowledge of the causative agent of HGE and of animal reservoirs in Europe is limited. Ixodes ricinus is a recognized vector of A. phagocytophilum in Europe. Prevalence of the agent in questing I. ricinus is usually higher in adult ticks than in nymphs and ranges from zero or very low to > 30%. Pronounced differences between countries and marked variability by localities were established. Up to March 2003 about 65 human patients (all but one were adults) with confirmed HGE and several patients fulfilling criteria for probable HGE had been reported. The majority of them came from Central Europe (Slovenia) and Scandinavia (Sweden) but there are individual reports from several other European countries. The patients presented with an acute febrile illness that as a rule occurred after a tick bite; the majority had leukopenia and/or thrombocytopenia, elevated concentration of C — reactive protein and mild abnormalities of liver function test results. A small number of patients does not permit reliable conclusions on the clinical features of European HGE; however, there is an impression that at least in central Europe (but maybe not in Scandinavia) the disease is, from the clinical angle, only mild to moderately severe and (most likely) self-limited.

The relatively high proportion of the population with HGE serum antibodies and the presence of A. phagocytophilum (like) agent(s) in ticks, small mammals and deer as found in several European countries are discordant with the rather low number of patients with proven HGE. The discordance may indicate inadequate awareness among European physicians, limited recording and reporting of the disease, and/or the presence of and the infection of humans with nonpathogenic A. phagocytophilum (like) strains present in ticks. Additional studies are needed to better define the biological and public health significance of HGE in Europe.

Tick-transmitted diseases like tick-borne encephalitis and Lyme borreliosis have been well known in Germany for decades. Ongoing research now gives an additional focus to a broad range of other bacteria and parasites in ticks like Anaplasma phagocytophilum, former Ehrlichia sp., Rickettsia sp. and Babesia sp. Knowledge about the prevalence of these infectious agents in ticks is an important prerequisite for risk assessment of human diseases. Therefore nymphs and adult Ixodes ricinus ticks were collected and examined for Anaplasma phagocytophilum (n = 5424 ticks), Rickettsia sp. (n = 1187), and Babesia sp. (n - 3113). For the detection of Anaplasma phagocytophilum, DNA from the 16S rDNA gene was amplified by nested PCR and hybridized with a DIG-labeled oligonucleotide probe. The examination of Rickettsia sp. was performed by single PCR. A partial sequence of the citrate synthase gene was amplified. As a target for the detection of Babesia sp., DNA from the 18S rDNA gene was amplified, also by single PCR. All positive PCR products were sequenced to control specificity.

Anaplasma phagocytophilum was detected by PCR in n = 103 (1.9%) out of 5,424 examined ticks from 11 investigation areas. However, not all positive PCR products hybridized using DIG-labeled oligonucleotide probe. Thus, the result of sequencing indicated that only 1.0% (n = 54) belonged to Anaplasma phagocytophilum and nearly half of these PCR products (0.9%) were identified as Wolbachia sp.

Rickettsia sp. in Ixodes ricinus ticks from 3 areas were found in n = 105 (8.9%) out of 1,187 ticks examined (range from 13.3% to 5.6%). Sequencing showed Rickettsia helvetica exclusively. In about 2.6% of Rickettsia-positive ticks, double infection with Anaplasma phagocytophilum was found.

Babesia sp. was detected in n = 31 (1.0%) out of 3,113 ticks examined, which originated from 4 different areas. By sequencing, n = 28 (90.0%) were identified as Babesia divergens. Three of all Babesia — positive ticks were identified as harboring Babesia microti.

The detection of Anaplasma phagocytophilum, Rickettsia sp. and Babesia sp. demonstrates their possible role as a source of human infection in Germany.

The three host-tick Ixodes (I.) ricinus is regarded as an important vector of tick-borne microorganisms pathogenic for humans in central Europe and is primarily known as the main vector of Borrelia (B.) burgdorferi and the virus causing tick-borne encephalitis (TBE), the most clinically relevant tick transmitted pathogens for humans in European countries. Furthermore, it is now well established that I. ricinus also transmits Ehrlichia (E.) phagocytophila, Babesia (Ba.) divergens, and Ba. microti, all agents of zoonotic infections in dear, sheep, cattle, dogs, and horses. In addition to their known zoonotic potential, recent molecular-epidemiological and seroepidemiological surveys as well as increasingly reported clinical cases of infections caused by these tick-borne organisms other than B. burgdorferi (TOBB) also strongly suggest a possible relevance of Babesia, Ehrlichia and Rickettsia for humans at risk in Europe. However, there are few medical microbiological investigations and epidemiological data on the distribution and relevance of Babesia for humans in our part of the northern hemisphere. There is also very little diagnostic and clinical knowledge on human babesiosis in many regions of Europe. Furthermore, sophisticated diagnostic tools designed for the reliable detection of the underlying pathogens, are not yet generally available to the microbiological laboratory. This review aims to provide basic information on human babesiosis and the most relevant causative pathogens of the disease in Europe and to draw attention to this parasitic infection as a possibly emerging and probably underdiagnosed disease in this part of the northern hemisphere.

Tick-borne encephalitis (TBE) is one of the most frequent arthropod-transmitted viral diseases in Europe. Different vaccines against TBE-virus have been developed; a thimerosal-free and also albumin-free vaccine [Ticovac® (Baxter Hyland Immuno, Vienna)] was approved in 2000. Contrary to previous experience, 779 cases of fever occurred following the first vaccination of children under 15 years of age and in 62 children febrile convulsions were even observed. Consequently, the composition of the vaccine was changed and albumin was again added [FSME-Immun® (Baxter Vaccines, Vienna)] in 2001. The new Encepur Kinder® (Chiron-Behring, Marburg) from 2002 is a TBE-vaccine for children without any protein as stabilizer but with a relatively high concentration of sucrose, while the former vaccine Encepur K® from 1991 contained polygeline as the stabilizer.

The induction of the immune system by the different TBE virus vaccines was compared in an in vitro test in order to find an explanation for the unexpected fever attacks. Whole blood was stimulated with complete vaccine suspension, and TNF-α, IL-1β, IL-6, and IL-8 were determined from heparin/EDTA-plasma and culture supernatants.

It was shown that Ticovac® and the new Encepur Kinder® can induce relatively high amounts of TNF-α and lower amounts of IL-1β. An increase of both cytokines was first observed following an incubation of 4 hours, with a maximum after 15 hours. Concentrations returned to base-line values within 26 hours. The behaviour of both cytokines correlates with the febrile phases in children up to two years old. Albumin or other proteins like polygeline and also immunoglobulins prevented a rise of cytokines.

During the period of 1993–2002 an increase and the remarkable changes in the incidence of tick-borne encephalitis (TBE) and Lyme borreliosis (LB) as well as annual activities of vector species were noticed.

The highest increase of TBE morbidity in Latvia has been observed in 1994 and 1995, and less expressed also in 1998 which was followed by a significant decrease during subsequent years. Whereas the highest peak of LB morbidity has been noticed in 1998 with only a minor decrease during subsequent years.

Two epidemiologically significant Ixodes tick species are common in Latvia. Ixodes ricinus L. spread in the western and central part of Latvia; but rarely and in small numbers also in the eastern part. Ixodes persulcatus P. Sch. seems to dominate only in the eastern part of the country. The changes of seasonal and annual activities of I. ricinus were observed in two types of monitoring sites — sylvatic and peridomestic, located in the central part of Latvia. Observations of I. persulcatus were made in the eastern districts.

Comparing geographically the Tick-borne diseases (TBD) incidence data for three tick distribution regions (I. ricinus dominated, I. persulcatus dominated and mixed regions), it was observed that the trend of annual changes in LB incidence during the last decade is almost of the same kind for all regions. Whereas TBE incidence extremes in 1994 and 1995 were observed almost only in I. ricinus dominated region.

The annual field-collected adult tick infection rate with TBE virus (TBEV) from 1993 to 2002 for I. ricinus adults varied between 1.7% and 26.6% and for I. persulcatus — between 0% and 37.3%. The infection level in ticks removed from humans was much higher and from 1998 to 2002 surpassed 30%. TBEV investigations of removed adults and nymphs in 2002 discovered a high TBEV prevalence also in I. ricinus nymphs (43%). Typing of TBE virus isolated from ticks and patient serum samples in collaboration with German and Swedish virologists revealed that all three TBEV subtypes were co-circulating in Latvia.

The mean annual tick infection rate with Borrelia burgdorferi s.l. analysed by means of a nested polymerase chain reaction of OspA gene fragment during the period of 1999–2001 was 18%–38% for I. ricinus adults and 25%–51% for I. persulcatus adults. Typing of Borrelia-positive DNA samples indicated that B. afzelii was dominant in Borrelia-positive I. ricinus (64.9%) and I. persulcatus (81.2%) followed by B. garinii (I. ricinus: 24.3%; in I. persulcatus: 14.5%).

Investigations of Ehrlichia phagocytophila genogroup (by nested PCR targeted the 16S rRNA gene) revealed the presence of Ehrlichia sp. in I. ricinus from the central part of Latvia. Obtained data on